Valve for a plastifying device

ABSTRACT

In a plastifying device, a valve member is provided on the leading end of a worm for regulating flow to an injection head. The valve is displaceable in the axial direction of the worm and it has a head portion on its leading end, the axis of which is offset from the axis of the worm so that, as the worm rotates, the head continuously affords a partial closure for the end of the bore containing the worm and effects a mixing action as the material is fed to the injection head.

United States Patent Inventor Armin Blumer Schwanden, Switzerland Appl.No. 828,117 Filed May 27, 1969 Patented May 18, 1971 AssigneeMaschinenfabrik und Giesserel Netstal AG Netstal, Switzerland PriorityMay 31, 1968 Switzerland VALVE FOR A PLASTIFYING DEVICE 11 Claims, 2Drawing Figs.

US. Cl 18/30, 18/ 12 Int. Cl 1329f 1/00 Field of Search 18/308 (Q),

(SM), (SR), 128 (E); 259/9, 10, 45, 46; 264/329 [56] References CitedUNITED STATES PATENTS 3,452,398 7/1969 Siegel 18/30 FOREIGN PATENTS476,748 5/1929 Germany 18/12(SE) 1,201,039 9/1965 Germany PrimaryExaminer-J. Spencer Overholser Assistant Examiner-Michael 0. SuttonAttorney-McGlew and Tuttle ABSTRACT: In a plastifying device, a valvemember is pro vitied on the leading end of a worm for regulating flow toan injection head. The valve is displaceable in the axial direction ofthe worm and it has a head portion on its leading end, the axis of whichis offset from the axis of the worm so that, as the worm rotates, thehead continuously affords a partial closure for the end of the borecontaining the worm and effects a mixing action as the material is fedto the injection head.

mama) nmslsn. 3578.741

INVENTOI? Armin Blumer ATTORNEYS.

VALVE FOR A PLASTIFYING DEVICE SUMMARY OF THE INVENTION The presentinvention is directed to a plastifying device with a worm feed and ablow back obturator for an injection molding machine for plasticsmaterials and, more particularly, it is directed to a valve membermounted on the leading end of the worm for regulating the flow of thematerial to an injection head.

In the past it has been known to provide a valve member on the leadingend of a worm feed within a plastifying cylinder. In its closedposition, the valve cooperates with a first seating surface near theoutlet end of the plastifying cylinder to prevent the material passingtherethrough from flowing backwardly. In its opened position, the valvereleases the material for flow through an injection head and, inaddition, it is used as a guide core for the material up to theinjection channel of a reduced cross section. Moreover, the valvecooperates with a second seating surface and limits the return path ofthe material within the plastifying cylinder.

The valve members, known in the past as blow back obturators, have aconical surface located adjacent the leading end of the worm whichcooperates with a corresponding conical surface on an inset ring withinthe plastifying cylinder. Extending axially through the inset ring is ashaft spaced from the worm and the shaft has a coaxial head mounted onits leading .end which extends to a conical point and has a number ofaxially extending parallel edge recesses. A surface on the head isadapted to cooperate with a corresponding end stop face on the insetring. In this valve member there is the disadvantage that the passage ofmaterial afforded by the edge recesses in the head restricts flowbecause it is divided into several paths which eventually mix or mergetogether in an inefficient manner. Further, the installation of thevalve member is complicated, since it has a larger diameter than that ofthe inset ring.

It is the primary object of the present invention to overcome, as muchas is possible, the disadvantages of the prior art by providing a valvemember which affords adequate mixture of the material being fed to theinjection head and also overcomes the problems of backflow within theplastifying cylinder.

Therefore, in accordance with the present invention, a valve member isprovided extending forwardly from a worm feed and having a head locatedon its leading end with its axis arranged eccentrically to the axis ofthe worm. The outside diameter of the head adjacent the inset ring has adiameter less than the inside diameter of the inset ring. As the valvemember is rotated with the worm the head affords a closure for only aportion of the annular passage through the inset ring. Moreover, theadjacent circumferential surfaces of the head and the shaft coincide atone point whereby at that point a continuation of the circumferentialsurfaces of the head is provided on the shaft.

Within the plastifying cylinder, the valve member is axiallydisplaceable between a closed position cutting off the flow of materialforwardly from the worm and an opened position in which the materialflows through the annular space between the inner surface of the insetring and the shaft of the valve member. In the opened position the headis seated against a transverse surface on the inset ring and, due to theeccentric or radially offset arrangement of the head, continuous flow ispermitted from the annular passageway and the overlapping arrangement ofthe head across a portion of the passageway guarantees a good mixingaction on the material issuing from the plastifying cylinder. Further,the arrangement and dimensions of the head also facilitate theinstallation of the valve member within the plastifying cylinder.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there are illustrated and described preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a partial side view, partly in section, of a plastifyingdevice illustrating one embodiment of the present invention; and

FIG. 2 is another view, similar to FIG. 1, of a plastifying deviceillustrating a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, the outlet or leadingend of a plastifying device is shown formed of a plastifying cylinder 1having a stop head la coaxially mounted at its outlet end. For purposesof describing the structure and operation of the present invention theend of the plastifying cylinder having the stop head la will be referredto as the leading end, that is, the left-hand end as viewed in FIG. 1and the opposite or right-hand end will be referred to as the trailingend or section.

At the outlet end of the plastifying device, an injection head 2 ismounted in coaxial arrangement on the stop head la and is attached in amanner well known in the art. The bore 3 of the cylinder 1 extends intothe stop head la providing a bore continuation 3a having the samediameter as within the cylinder. Intermediate the axial length of thestop head lathe bore tapers from continuation 3a through a frustoconicalportion 4 to a cylindrically shaped outlet portion 5a at its leadingend. The outlet passageway 5 from the stop head leads into an injectionchannel 6 within the injection head 2.

Fitted within the leading end of the bore 3 of the plastifying cylinder1 is an inset sleeve 7 whose outer surface contacts the inner surface ofthe bore 3 and the opening through the sleeve affords a continuation ofthe bore 3 leading into the bore continuation 3a within the stop headla. At its trailing end the inset sleeve 7 has a frustoconically shapedsurface 7a tapering inwardly toward the outlet end of the cylinder 1. Atthe opposite or leading end of the inset sleeve 7, it has an annularsurface 7b disposed in a plane perpendicular to the axis a of thecylinder 1.

A plastifying worrn 8 is positioned within the cylinder 1 rearwardlyfrom the inset sleeve and is arranged therein in a known manner. Fromthe leading end of the worm 8, a valve member 9 extends forwardly intothe stop head la passing through the bore or passageway provided by theinset sleeve 7. Adjacent its connection to the worm 8, the valve 9 has afrustoconical surface 9a facing toward the leading end of theplastifying device and tapering inwardly from a diameter correspondingto the core diameter of the worm to a diameter somewhat smaller than theinside diameter of the inset sleeve 7. The angle of the surface 9acorresponds to that of the seat or inlet surface 7a at the trailing endof the inset sleeve 7. A shaft 9b, coaxial with the worm or cylinder,extends from the smaller diameter end of the surface 9a through theinset sleeve 7 to the stop head 1a end of the cylinder 1. Since theshaft 9b has a smaller diameter than the inset sleeve and is arrangedcoaxially within the cylinder 1, a concentric annular passageway isprovided about the shaft through the inset sleeve. Mounted on theleading end of the shaft 9b is a valve head which extends forwardly intothe stop head 12. The head 90 is symmetrically arranged about its axis bwhich is eccentric to or radially offset from the axis a of the cylinderand worm. At its end connected to the shaft the head is formed by acylindrically shaped section which projects forwardly into the stop headlaand extending axially from the cylindrical section is a conicalsection and the angle of cone corresponds to the angle of the oppositelydisposed frustoconical surface 4 within the stop head 12:. As indicatedin FIG. 1, the conical surface on the head 90 is spaced inwardly fromthe opposed surface 4 of the stop head.

In addition to the eccentric arrangement of the axis b of the head 9crelative to the axis a of the worm and the shaft, the diameter of thecylindrical section of the head is somewhat smaller than the insidediameter of the inset sleeve 7. In addition, the relationship of theeccentricity of the axesa,b and the relative diametrical dimensions ofthe interior of the inset sleeve and of the cylindrical section of thehead are arranged so that the circumferential surfaces of the shaft andthe cylindrical section of the head coincide at one point and at thislocation afford a continuous line from the circumferential surface ofthe shaft 9b to the circumferential surface of the cylindrical sectionof the head 90. In FIG. 1, this characteristic of the circumferentialsurfaces can be noted by the continuous line formed by the shaft and thehead on the lower side of the axis a.

At its trailing end, the head 90 has a transverse surface 9d extendingperpendicularly to the axis of the shaft and extending from the shaftoutwardly beyond the inner surface of the inset sleeve 7. The valvemember 9 is axially displaceable through the inset sleeve and, in aclosed position, as shown in FIG. 1, its frustoconical surface 9acontacts the correspondingly shaped surface 7a on the inset sleeve whilein its opened position the frustoconical surfaces 7a and 9a are spacedapart and the surface 9d rests against a portion of the surface 7b atthe leading end of the inset sleeve. Accordingly, in the openedposition, as the worm and valve member rotate, the surface 9d of theeccentrically arranged head 90 traces a path about the annular surface7b of the inset sleeve 7. Accordingly, an orifice is provided from theannular passageway between the inner surface of the sleeve and the shaftwhich has a crescent or sickle-shaped section for admitting the materialpassing through the plastifying cylinder into the bore continuation 3ain the stop head Ia. As the valve member 9 rotates the orifice from theannular passageway moves about the outlet end of the sleeve so that theinjection molding material undergoes a thorough mixing as it enters thestop head la. Moreover, the offset arrangement of the head 90 within thestop head Ia and the variable spacing between the surface 4 of the stophead and the oppositely disposed surface of the valve head also effectsimproved mixing.

In FIG. 2, an embodiment generally similar to the plastifying deviceshown in FIG. 1, is exhibited, however, the axial relationship of thehead and shaft of the valve member relative to the axis of the worm aredifferent. In FIG. 2, a portion of a plastifying cylinder 11 is showncontaining an inset sleeve 17 adjacent its leading end with a valvemember 19 extending through the inset sleeve in a manner generallysimilar to that shown in FIG. I. At the trailing end the inset sleevehas a frustoconical surface 170 which cooperates with a correspondingfrustoconical surface 19a on the end of the valve member 19 adjacent theworm, not shown. The axis of the trailing end of the valve member 19 iscoaxial with the axis a of the bore 13 through the cylinder 11. At theleading end of the inset sleeve, an annular surface 17b is providedarranged in a plane perpendicular to the axis a of the bore 13. Thevalve head 19c has a configuration similar to that shown in FIG. 1, thatis, a cylindrical section extending from the shaft 1% with a conicalsection mounted on the cylindrical section. The trailing surface 19d ofthe cylindrical section of the head 190 is arranged in a planeperpendicular to the axis a of the bore 13 and is in parallelrelationship with corresponding surface 17b of the inset sleeve. Thevalve member is axially displaceable through the inset sleeve from aclosed position with the frustoconically shaped surfaces 170, 19a incontact to an opened position with the surface 19d of the valve headresting against the surface 17 b of the inset sleeve.

In FIG. 1, the axis of the shaft 91) of the valve member coincides withthe axis of the worm 8, however, in the embodiment shown in FIG. 2, theaxis c of the shaft 1% is offset from the axis a of the worm and theaxis b of the head 19c is offset not only with respect to the axis a butalso with respect to the axis of the shaft. All three of the axes a, b,and 0 lie in a common plane with the axis b being located radiallyoutwardly from the axis a beyond the axis c. As with the embodiment setforth in FIG. 1, the relationship of the diameter of the cylindricalsection of the head 19c and the diameter of the shaft 14b is arranged sothat at one point their circumferential peripheries coincide and acontinuous line is provided from the circumferential surface of thecylindrical section of the head to the circumferential surface of theshaft 17b. Further, the diameter of the cylindrical section of the headis slightly less than the inside diameter of the inset sleeve tofacilitate its installation within the plastifying device.

Due to the dual eccentricity of the shaft and head of the valve member19 with respect to the axis a of the worm, the injection materialflowing through the cylinder 11 is mixed both on its passage from theannular passageway between the inset sleeve and the shaft and within theannular passageway since the spacing between the shaft and the innersurface of the inset sleeve is continuously changing as the valve memberrotates.

. In the embodiments disclosed above a more effective mixing is obtainedthan was possible in the past with the use of slots or screwlikepassages on the head of the valve member. Further, since the diameter ofthe cylindrical section of the head is slightly less than the insidediameter of the inset sleeve and because of the eccentric arrangement ofthe head, the manufacture and assembly of the valve member isfacilitated and the valve member is capable of acting effectively as ablow back obturator.

I claim:

1. In a plastifying device, for an injection molding machine, comprisinga plastifying cylinder having an axially extending bore therethrough,said cylinder having a leading end and a trailing end, an inset ringcoaxially fitted within the bore of said cylinder adjacent the leadingend thereof and said inset sleeve forming an axially aligned passagewayproviding a continuation of the bore within said cylinder, a worm memberrotatably mounted within the bore in said cylinder and positionedrearwardly of said inset sleeve, and wherein the improvement comprises avalve member attached to the leading end of said worm, said valve membercomprising a shaft extending through said inset sleeve from the trailingend to the leading end thereof, said shaft being spaced inwardly fromthe surface of the passageway through said inset sleeve and formingtherewith an annular flow path, a head affixed to the leading end ofsaid shaft and being positioned forwardly of the leading end of saidinset sleeve, the axis of said head being in parallel relationship withand arranged eccentrically to the axis of the bore through said cylinderand the trailing end of said head having a dimension transverse to theaxis of the passageway through said inset sleeve so that a portion ofthe outer periphery of said head extends radially outward from the innersurface of said inset sleeve and another portion of the outer peripheryof said head is spaced radially inwardly from the inner surface of saidinset sleeve whereby with the trailing end of said head and the leadingend of said inset sleeve in contact a portion of the annular flow pathbetween said shaft and the inner surface of said inset sleeve is open asthe valve member rotates on the end of said worm so that a continuousmixing action is obtained as the materials flow upwardly from theleading end of said inset sleeve about said head.

2. A plastifying device, as set forth in claim 1, wherein said head ofsaid valve member being secured to said shaft so that thecircumferential periphery of said head adjacent said shaft coincideswith a point on the circumferential periphery of said shaft whereby acontinuous line on the circumferential periphery of said shaft arrangedin parallel relationship with the axis of the bore extends through thepoint of coincidence and continues on the circumferential surface ofsaid head.

3. A plastifying device, as set forth in claim 2, wherein the trailingend of said head having a cylindrical form and having a diameter whichis less than the inside diameter of said inset sleeve.

4. A plastifying device, as set forth in claim 3, wherein said shaftbeing coaxially arranged within said cylinder.

5. A plastifying device, as set forth in claim 3, wherein the axis ofsaid shaft being arranged eccentrically to the axis of said cylinder andthe axis of said head being arranged eccentrically to the axis of bothsaid cylinder and said shaft, with the axes of said head, said shaft andsaid cylinder being arranged in a common plane and the axis of saidshaft being positioned between the axes of said cylinder and said head.

6. A plastifying device, as set forth in claim 3, wherein said insetsleeve having a frustoconically shaped surface at its trailing endextending transversely to the axis of said cylinder and having anannular surface at its leading end disposed in a plane arrangedperpendicularly to the axis of said cylinder.

7. A plastifying device, as set forth in claim 6, wherein said headhaving a'trailing surface disposed transversely to the axis of saidcylinder and being in parallel relationship with the leading end annularsurface of said inset sleeve.

8. In a plastifying device, as set forth in claim 6, wherein said valvemember comprising a transition section extending from the trailing endof said shaft to said worm, said transition section having afrustoconically shaped surface diverging inwardly from the diameter ofsaid worm, and said frustoconical surface having a cone anglecorresponding to the cone angle of the frustoconical surface on thetrailing end of said inset sleeve, whereby the corresponding saidfrustoconical surfaces can be placed in contact forming a closure forthe bore through said cylinder at the trailing end of said inset sleeve.

9. In a plastifying device, as set forth in claim 3, wherein said headhaving a cylindrically shaped section extending forwardly from saidshaft, and a conically shaped section extending forwardly from saidcylindrically shaped section.

10. In a plastifying device, as set forth in claim 9, wherein a stophead being affixed to the leading end of said cylinder and having a boretherethrough forming a continuation of the bore through said cylinder,an injection head fitted to the leading end of said stop head and beingcoaxial with said stop head and said cylinder, and said injection headproviding a passageway forming a continuation of the bores through saidstop head and cylinder.

11. In a plastifying device, as set forth in claim 10, wherein the borewithin said stop head having a first section having the same diameter asthe bore at the end of said cylinder and a second section extendingforwardly therefrom having a frustoconical shape surface, the conicallyshaped surface of said head of said valve member being disposed withinthe bore in said stop head and having its conical surface disposed invariably spaced relationship relative to the frustoconically shapedsurface in the bore of said stop head.

1. In a plastifying device, for an injection molding machine, comprising a plastifying cylinder having an axially extending bore therethrough, said cylinder having a leading end and a trailing end, an inset ring coaxially fitted within the bore of said cylinder adjacent the leading end thereof and said inset sleeve forming an axially aligned passageway providing a continuation of the bore Within said cylinder, a worm member rotatably mounted within the bore in said cylinder and positioned rearwardly of said inset sleeve, and wherein the improvement comprises a valve member attached to the leading end of said worm, said valve member comprising a shaft extending through said inset sleeve from the trailing end to the leading end thereof, said shaft being spaced inwardly from the surface of the passageway through said inset sleeve and forming therewith an annular flow path, a head affixed to the leading end of said shaft and being positioned forwardly of the leading end of said inset sleeve, the axis of said head being in parallel relationship with and arranged eccentrically to the axis of the bore through said cylinder and the trailing end of said head having a dimension transverse to the axis of the passageway through said inset sleeve so that a portion of the outer periphery of said head extends radially outward from the inner surface of said inset sleeve and another portion of the outer periphery of said head is spaced radially inwardly from the inner surface of said inset sleeve whereby with the trailing end of said head and the leading end of said inset sleeve in contact a portion of the annular flow path between said shaft and the inner surface of said inset sleeve is open as the valve member rotates on the end of said worm so that a continuous mixing action is obtained as the materials flow upwardly from the leading end of said inset sleeve about said head.
 2. A plastifying device, as set forth in claim 1, wherein said head of said valve member being secured to said shaft so that the circumferential periphery of said head adjacent said shaft coincides with a point on the circumferential periphery of said shaft whereby a continuous line on the circumferential periphery of said shaft arranged in parallel relationship with the axis of the bore extends through the point of coincidence and continues on the circumferential surface of said head.
 3. A plastifying device, as set forth in claim 2, wherein the trailing end of said head having a cylindrical form and having a diameter which is less than the inside diameter of said inset sleeve.
 4. A plastifying device, as set forth in claim 3, wherein said shaft being coaxially arranged within said cylinder.
 5. A plastifying device, as set forth in claim 3, wherein the axis of said shaft being arranged eccentrically to the axis of said cylinder and the axis of said head being arranged eccentrically to the axis of both said cylinder and said shaft, with the axes of said head, said shaft and said cylinder being arranged in a common plane and the axis of said shaft being positioned between the axes of said cylinder and said head.
 6. A plastifying device, as set forth in claim 3, wherein said inset sleeve having a frustoconically shaped surface at its trailing end extending transversely to the axis of said cylinder and having an annular surface at its leading end disposed in a plane arranged perpendicularly to the axis of said cylinder.
 7. A plastifying device, as set forth in claim 6, wherein said head having a trailing surface disposed transversely to the axis of said cylinder and being in parallel relationship with the leading end annular surface of said inset sleeve.
 8. In a plastifying device, as set forth in claim 6, wherein said valve member comprising a transition section extending from the trailing end of said shaft to said worm, said transition section having a frustoconically shaped surface diverging inwardly from the diameter of said worm, and said frustoconical surface having a cone angle corresponding to the cone angle of the frustoconical surface on the trailing end of said inset sleeve, whereby the corresponding said frustoconical surfaces can be placed in contact forming a closure for the bore through said cylinder at the trailing end of said inset sleeve.
 9. In a plastifying device, as set forth in claim 3, wherein said head having a cylindrically shaped section extending fOrwardly from said shaft, and a conically shaped section extending forwardly from said cylindrically shaped section.
 10. In a plastifying device, as set forth in claim 9, wherein a stop head being affixed to the leading end of said cylinder and having a bore therethrough forming a continuation of the bore through said cylinder, an injection head fitted to the leading end of said stop head and being coaxial with said stop head and said cylinder, and said injection head providing a passageway forming a continuation of the bores through said stop head and cylinder.
 11. In a plastifying device, as set forth in claim 10, wherein the bore within said stop head having a first section having the same diameter as the bore at the end of said cylinder and a second section extending forwardly therefrom having a frustoconical shape surface, the conically shaped surface of said head of said valve member being disposed within the bore in said stop head and having its conical surface disposed in variably spaced relationship relative to the frustoconically shaped surface in the bore of said stop head. 